基坑開挖對坑底工程樁性能影響參數(shù)分析*
鄭剛1,2，王琦1,2，張立明3
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（1 濱海土木工程結(jié)構(gòu)與安全教育部重點(diǎn)實(shí)驗(yàn)室（天津大學(xué)）， 天津 300072；2 天津大學(xué)建筑工程學(xué)院， 天津 300072； 3 天津市地下鐵道集團(tuán)有限公司， 天津 300051）
［摘要］基坑開挖對坑內(nèi)工程樁的影響不可忽視。基于工程試樁實(shí)測資料驗(yàn)證的有限元參數(shù)，對不同基坑開挖深度及平面尺寸條件下坑底不同位置處單樁的工作特性進(jìn)行參數(shù)分析。分析表明，基坑開挖導(dǎo)致較大的樁身初始拉力，樁身最大初始拉力值可達(dá)到將近地面試樁承載力的50%，樁身最大相對初始拉力隨著基坑開挖寬度（B）與開挖深度（H）的比值增大而增大；當(dāng)樁長（L）與基坑開挖深度（H）的比值為2～3時(shí)，樁身最大相對初始拉力出現(xiàn)最大值。樁身最大初始拉力相對位置基本上隨L/H增加而減小，隨B/H增加而增加。單樁剛度大多有所降低，最嚴(yán)重時(shí)可減小到原來的26.4%，對于L/H和B/H均較小的情況，相對剛度可能出現(xiàn)大于1的情況?；娱_挖引起的樁身最大初始拉力及其所在位置和單樁剛度的降低在設(shè)計(jì)中應(yīng)加以考慮。［關(guān)鍵詞］基坑開挖; 單樁; 樁身初始拉力; 相對剛度; 參數(shù)分析中圖分類號：TU473.1 文獻(xiàn)標(biāo)識碼：A 文章編號：1002-848X(2015)21-0063-07
Parametric analysis on influence of foundation pit excavation on the performance of pit bottom pilesZheng Gang1,2, Wang Qi1,2, Zhang Liming3(1 Key Laboratory of Coast Civil Structure Safety (Tianjin University), Ministry of Education, Tianjin 300072, China; 2 School of Civil Engineering, TianjinUniversity, Tianjin 300072, China; 3 Tianjin Metro Group Co., Ltd., Tianjin 300051, China)Abstract: The influence of foundation pit excavation on the performance of pit bottom piles should not be ignored. Based on the measured data verified finite element parameters of the project piles, parametric analysis was carried out on working performance of a single pile in different pit bottom locations under conditions of different foundation pit excavation depths and excavation plane dimensions. The finite element analysis shows that large initial tensile force may occur due to foundation pit excavation and the maximum initial tensile force of pile shaft can be 50% of the bearing capacity of the ground test pile. The maximum relative initial tensile force of pile shaft increases with the growth of the ratio of foundation pit excavation depth(B) and foundation pit excavation width(H). The maximum value of the maximum relative initial tensile force occurs when the ratio of pile length(L) and foundation pit excavation width(H) is 2～3. The relative position of maximum initial tensile force of pile shaft mainly decreases with the increase of L/H, and increases with the growth of B/H. Most of the stiffness of single piles decreases after excavation, and the minimum value can be 26.4% of the initial value. The relative stiffness may be larger than 1 when both of L/H and B/H are small. The maximum initial tensile force of pile shaft due to excavation and its position should be taken into consideration in design as well as the decrease of the single pile stiffness.Keywords: foundation pit excavation; single pile; initial tensile force of pile shaft; relative stiffness; parametric analysis*國家自然科學(xué)基金資助項(xiàng)目（50878144），國家重點(diǎn)基礎(chǔ)研究發(fā)展計(jì)劃（973計(jì)劃）資助項(xiàng)目（2010CB732106）。作者簡介：鄭剛，博士，教授，博士生導(dǎo)師，Email:zhenggang1967@163.com。
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